Double chain jack

ABSTRACT

A single jack ram is straddled by two chains resulting in low cost and a balanced load. Ram head latches and cylinder assembly latches are formed as double pins hydraulically operated and which are oriented at right angles to each other to engage consecutive links of the chain when the ram is completely retracted. This eliminates possible misregister of the latches, caused by cumulative pitch error from manufacturing or stretch in operation, if the latches are separated by several links of the chain.

United States Patent. 11 1 Chambers Jan. 7, 1975 DOUBLE CHAIN JACK2,996,284 8/1961 Welbom 254/107 Inventor: Henry B. Chambers Santa Inez,3,499,629 3/1970 Horton 1. 254/93 R Cahf' Primary Examiner-Al LawrenceSmith [73] Assignee: Hydranautics, Santa Barbara, Calif. As istantExaminer-Robert C. Watson [22] Filed June 13 1972 Attorney, Agent, orFirm-Clement H. Allen [21] Appl. N0.: 369,517 [57] ABSTRACT A singlejack ram is straddled by two chains resulting 521 US. Cl. 254/108 in lowcost and a balanced laad- Ram head latches and 51 Int. Cl B66f 1/08Cylinder assembly lalahaa are fahhad as lauhla Pins [58] Field of Search254/93 R 105-111 hydraulically Operated and which are Orlamad at right 7angles to each other to engage consecutive links of the [56] ReferencesCited chain when the ram is completely retracted. This eliminatespossible misregister of the latches, caused by UNITED STATES PATENTScumulative pitch error from manufacturing or stretch 2 i f in operation,if the latches are separated by several am 2,609,953 9/1952 Schramm254/93 R lnks of the chem" 2,973,566 3/196l Elsner 254/93 R 4 Claims, 5Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to an improved chain jack, and more particularlyto a chain jack having a double chain.

2. The Prior Art A number of chain jacks have been proposed and used bythe prior art featuring designs for lifting heavy loads with equal orbalanced load distribution. Double ram jacks have employed a singlechain between the rams which are actuated by hydraulic cylinders. Singleram jacks with a side arm and parallel single chain are inherentlyunbalanced but can be used for relatively light loads, and if the ram ismaintained aligned by a spaced apart bearing couple in the hydrauliccylinder to counteract the effect of the side load.

This invention provides a balanced load chain jack which can beconstructed at low cost and which features more accurate register oflifting and holding latches with the links of the chain. Additionallythe jack allows complete disassembly of the hydraulic piston andcylinder assembly while the load is suspended by the holding latches.

BRIEFSUMMARY OF THE INVENTION Summarized briefly, this inventioncomprises a chain jack having a single ram repetitively actuated by ahydraulic cylinder with latch plates attached to the ram head and to thehydraulic cylinder. Each of the latch plates has cruciform apertures onopposite sides of the ram, the apertures in the ram head latch platebeing aligned with the corresponding apertures in the cylinder latchplate. A pair of chains, one on each side of the ram, pass through eachpair of aligned cruciform apertures with their top ends, for operationin vertical position, being passed over sheaves mounted on the ram headlatch plate. Latches to engage links of the chains are arranged in theram head and in the plate attached to the cylinder. These latches areoriented at right angles to each other and engage the chains at adjacentor consecutive links when the ram actuating piston is fully retractedinto the hydraulic cylinder.

The latches are each formed as a pair of pins actuated in and out ofengagement with the chains by hydraulic cylinders which may be manuallyor automatically controlled by conventional apparatus for lift or lowermode of operation. The latch pins of each pair, when engaged with thechain lie, against under portions of a chain link on each side of theadjacent link, the pins being flattened in their areas of contact withthe chain link surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS Construction and operation of thisinvention will be apparent from the following description thereof andfrom the annexed drawings in which:

FIG. 1 is a general isometric view of a chain jack embodying features ofthis invention.

FIG. 2 is a general side view of the chain jack of FIG. 1, withouthydraulic auxiliary equipment.

FIG. 3 is a horizontal section of the chain jack of FIG. 2 taken alongthe line 3-3 of FIG. 2.

FIG. 4 is a horizontal section of the chain jack of FIG. 2 taken alongthe line 44 of FIG. 2.

FIG. 5 illustrates a latch pin assembly showing flattened surfaces forcontact with a chain link.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now particularly toFIGS. 1 to 4 the chain jack comprises a hydraulic cylinder in whichrides a piston 12 to which is attached ram 14. Proximate the top ofcylinder 10 is attached lower latch plate I6 which, as will be seen bestin FIG. 4 has a pair of cruciform apertures 18 on opposite sides of ram14. The top of hydraulic cylinder 10 terminates slightly above latchplate 16 and is provided with seal member 20 and hearing plate 22.

To the head 24 of ram 14 is attached upper latch plate 26 also providedwith a pair of cruciform apertures l8 vertically aligned with similarapertures 18 in cylinder latch plate 16. The apertures in latch plate 26are best seen in FIG. 3.

Fixedly attached to the top of latch plate 26 are two pairs ofdiverging, outwardly extending, spaced-apart supports 28. Shafts 30 arejournalled through the outer ends of each pair of supports 28 and carryfreely rotable grooved sheaves 32. A chain 34 is carried over each ofsheaves 32, having its free end as at 36 simply hanging to provideweight to keep chain 34 in place on sheave 32 and passing throughaligned apertures 18 in latch plates 26 and 16.

As will be seen more clearly in FIG. 3 upper latch plate 26 is arrangedwith two pairs of parallel spaced apart latch pins 38 which are slidablymounted in horizontal holes in latch plate 26, these holes being in theway of apertures 18 with each hole on one side of the center-slot forpassage of a chain link in the end-on position. The outer ends of eachpair of latch pins 38 are attached to a mount plate 40 attached to ahydraulic cylinder 42 with its extending piston rod slidably passingthrough mount plate 40 and having its end attached to the edge of latchplate 26 as shown.

As will be seen more clearly in FIG. 4, lower latch plate 16 is alsoarranged with two pairs of parallel spaced apart latch pins 38 which areslidably mounted in horizontal holes in the way of apertures 18 with ahole being on each side of the center slot for passage of a chain linkin the end-on position. The outer ends of each pair of latch pins 38 areattached to a mount plate 40 to which is attached a hydraulic cylinder42 with its extending piston rod slidably passing through mount plate40, and having its end attached to the edge of latch plate 16 as shown.As will be seen in FIG. 5 latch pins 38 are fabricated with flattenedareas 39 where they contact the links of chains 34.

Operation of latch pins 38 is controlled by hydraulic systemsillustrated diagramatically in FIG. I and which cause latch pins 38 tobe moved inwardly, alongside both sides of end-on links in chains 34 andunder the lower side portions of the adjacent cross chain linkimmediately above, or outwardly, clear of apertures 18. The hydrauliccylinders 42 in operating latch pins 38 in upper latch plate 26 areactuated simultaneously by exerting oil pressure on either side of theirpistons 44 through oil lines 46 or 48 by high pressure pump 50. Thereturn drain is connected to oil reservoir 52, the oil and drain lineconnections being made to oil lines 46 and 48 selectively by manuallyoperated 4 way valve 54. In like manner hydraulic cylinders 42 causelatch pins 38 to move inwardly in the way of apertures 18 in lower latchplate 16, or outwardly clear of these apertures as previously describedfor those in upper latch plate 26. The hydraulic cylinders 42 actuatingpins 38 in latch plate 16 are similarly connected in pairs to another 4way valve 54a with a high pressure pump 50a and an oil reservoir 52 a byconnecting oil lines 56 and 58. It will be understood that the hydraulicsystems are illustrated diagramatically for clarity, and that additionalconventional equipment and controls may be employed and also thathydraulic lines 46 and 48 as well as 56 and 58 will be sufficientlyflexible to allow in and out movement of latch pins 38, their mountplates 40 and hydraulic cylinders 42.

Piston 12 connected to ram 14 is actuated in cylinder by connection ofoil lines 60 and 62 to cylinder 10 above and below piston 12 with oilbeing introduced selectively under pressure to one side by another highpressure pump 64, the other side being connected to drain into reservoir66, the up or down action of piston 12 and attached ram 14 beingcontrolled by direction of the pressurized oil flow by another 4 wayvalve 68.

A position indicator in the form of a hanging scale stick may beattached to the underside of upper latch plate 26 and allowed to rideslightly against a visible sharp edge of lower latch plate 16. Indiciaon the scale stick can be arranged to show the precise position of upperlatch plate 26 relative to lower latch plate 16 so that one or the otherset of latch pins can be moved inwardly to support the load on selectedchain links.

For simplicity and ease of understanding the chain jack of thisinvention has been illustrated and described to be operated by manuallycontrolled hydraulic systems, specifically by valves 54 and 54acontrolling the in and out movement of the latches and valves 68controlling the up and down movement of the ram 14. For example, forlift mode of operation assuming the chains 34 carrying a load to besupported by latch pins 38 in their inward position in lower latch plate16 (as shown in FIG. 2) then the ram 14 is retracted by operation ofvalve 68 until the marks on scale stick 70 indicate that the latch pins38 in upper latch 26 are registered properly just below the bottom ofthe cross links of chains adjacent to and immediately above the linkssupported by the latch pins in lower latch plate 16. Valve 54 is thenturned to introduce pressurized oil into the outer ends of upper latchplate cylinders 42 so that latch pins now are run in and then latch pins38 in lower latch 16 are retracted by operation of valve 54a so that thechains and the load are supported by the upper latch plate 26.

The upper latch plate 26 may now be raised by introduction ofpressurized oil into the bottom of hydraulic cylinder 10 by suitableadjustment of valve 68, and will raise the chains 34 and the load. Whenupper latch plate 26 has been raised the distance of say one link asindicated by the marks on scale stick 70 the upward movement of ram 14is stopped by rotating valve 68 to a neutral position then valve 54a isactuated to cause latches 38 in lower latch plate 16 to be moved inwardunder the bottom sides of the selected link of chain 34 which will be inproper register because of the alignment indicated by the position ofscale stick 70. Ram 14 is then lowered slightly until the load is pickedup by the latches 38 in lower latch plate 16 and then latch pins 38 inupper latch plate 26 are retracted and the upper latch plate 26 islowered by operation of valve 68 until upper latch plate 26 is inposition so that its latches 38 may be moved inward again under thebottom sides of the links of chains 34 immediately above those engagedby the latch pins in lower latch plate 16. The lift cycle is repeated toraise the chain (and the load) the desired height, withexcess chainhanging over sheaves 32.

For lower mode by operation, the load is first lifted slightly onlatches 38 in upper latch plate 26, the latches 38 in the lower latchplate 16 are retracted and the ram and upper latch plate carrying theload is then lowered by operation of valve 68 to allow oil to be forcedinto reservoir 66 by piston 12 in cylinder 10. When the upper latchplate has been lowered until proper register has again been achieved (asindicated by scale stick 70) latches 38 in lower latch plate 16 aremoved inwardly to catch and support the load. Latch pins 38 in upperlatch plate 26 are then retracted and upper latch plate 26 with itschain and sheave assembly are again raised for another lowering strokeand the cycle repeated.

While the ram and latch operation of the chainjack of this invention hasbeen illustrated as being manually controlled it will be understood thatelectrical, hydraulic, mechanical, or other type of automatic controlmeans may be employed to provide repetitive actuation of the ram liftand lower hydraulic cylinder, and the hydraulic cylinders actuating thelatch pins in both latch plates. Such automatic control means may use acam and follower arrangement, or other device to provide properly spacedactuation of the control valves.

The double chain jack of this invention is advantageous in that a singlehydraulic cylinder and ram is employed between a pair of chains.Therefore the load on the ram and the hydraulic cylinder is balanced andis wholly vertical. This makes possible the simplest form of hydraulicactuating equipment without need for providing devices to counteractside or off-center loads. Thus the ram, the cylinder and ram andassociated structure may be considerably lighter and less expensive thanif side or off-center loads would have to be counteracted. A single ramarrangement with balanced load is of course of substantially lower costthan employment of a double ram assembly proposed and used by the priorart.

The cylinder latch plate can be constructed of heavy material to serveas a convenient mount for the jack. This will allow complete disassemblyof the cylinder and its piston, and the ram assembly, while the load issupported by the latches in the cylinder latch plate. This is amaintenance advantage in event of a seal leak.

The latch pins as described are preferably fabricated of cylindrical barstock with flat surfaces in the areas that the pins contact the chainlinks. This provides a greater area of surface contact and distributionof load over both sides of the chain. The chain jack with chain loadsnot biased, that is with loads evenly distributed between the twochains, may be used for operation in horizontal attitude in which casethe sheaves carrying the chains may not be used. For horizontaloperation where the load may be required to be pushed or pulled,

the latch pins 38 are preferably fabricated with flattened areas on twoopposite sides as specifically illustrated in FIG. 5. The surfaces ofthe chain links, will, after a period of rise under heavy load, becomethemselves slightly upset and flattened at areas of contact with thelatch pins. This will not detract materially from the chain linkstrength and will provide better and more even load support.

Employment of the bar type latches contacting the undersides of thelinks of the chain is additionally advantageous because thisorganization permits use of chains assembled from links each having acentralcross bar and often referred to as stud-link chain. This type isstronger than plain welded link chain. The latches, produced from roundbar stock are strong and inexpensive to fabricate, and their flattenedsurface, as described, provide areas for effective distribution of thelifting or moving loads.

Orientation of the two sets of latch pins so that these are at rightangles, and close together, is of substantial importance. This permitsthe two sets of latches to engage adjacent chain links and eliminatesmis-register that often occurs when spaced apart latches engage a chainat intervals of several links. If latches are separated by several linksat their closest position, that is when the ram is fully retracted inthe hydraulic cylinder, cumulative pitch error from manufacturing orchain stretch can cause mis-register of the latches with the chainlinks. With the latches oriented as described and the latch platesarranged so that the latches will en gage adjacent latches at theirclosest position, the possibility of mis-register of the latches withthe chain links is essentially eliminated at the important position atwhich the raising latch engages the chain for a lifting stroke.

I claim:

1. A chain jack having a chain, a pair of latch plates having latchesfor selectively engaging and disengaging the links of said chain, meansfor moving the said latch plates repetitively from and toward eachother, and means for actuating said latches in and out of engagementwith the links of said chain, in which the improvement comprises:

a. a single ram connected to a piston in a hydraulic cylinder;

b. a latch plate attached to the head of said ram and a latch plateattached to said hydraulic cylinder, said latch plates each having twocruciform apertures, one on each of opposite sides of said ram, thecruciform apertures in the said ram head latch plate being verticallyaligned with the corresponding cruciform apertures in the said cylinderlatch plate;

0. two chains passing through said cruciform apertures, one on each ofopposite sides of said ram;

d. two pairs of parallel spaced apart latch pins slidably mounted inhorizontal holes in each of said latch plates, a pair on each ofopposite sides of said ram and in the way of said cruciform aperturesfor selectively engaging and disengaging said chains passing throughsaid cruciform apertures; and

e. means for repetitively extending and retracting said ram in saidhydraulic cylinder and means for engaging and disengaging said latchpins from said chains to cause lifting and lowering of said chains.

2. A chain jack according to claim 1 in which the upper free ends ofsaid chains pass over sheaves rotatably mounted on said ram head latchplate.

3. A chainjack according to claim 1 in which the said latch pins in saidlatch plate attached to said ram are oriented at right angles to thesaid latch pins in the said latch plate attached to said hydrauliccylinder.

4. A chain jack according to claim 1 in which said latch pins arecylindrical with flattened surfaces at their areas of contact with thesurfaces of the links of said

1. A chain jack having a chain, a pair of latch plates having latchesfor selectively engaging and disengaging the links of said chain, meansfor moving the said latch plates repetitively from and toward eachother, and means for actuating said latches in and out of engagementwith the links of said chain, in which the improvement comprises: a. asingle ram connected to a piston in a hydraulic cylinder; b. a latchplate attached to the head of said ram and a latch plate attached tosaid hydraulic cylinder, said latch plates each having two cruciformapertures, one on each of opposite sides of said ram, the cruciformapertures in the said ram head latch plate being vertically aligned withthe corresponding cruciform apertures in the said cylinder latch plate;c. two chains passing through said cruciform apertures, one on each ofopposite sides of said ram; d. two pairs of parallel spaced apart latchpins slidably mounted in horizontal holes in each of said latch plates,a pair on each of opposite sides of said ram and in the way of saidcruciform apertures for selectively engaging and disengaging said chainspassing through said cruciform apertures; and e. means for repetitivelyextending and retracting said ram in said hydraulic cylinder and meansfor engaging and disengaging said latch pins from said chains to causelifting and lowering of said chains.
 2. A chain jack according to claim1 in which the upper free ends of said chains pass over sheavesrotatably mounted on said ram head latch plate.
 3. A chain jackaccording to claim 1 in which the said latch pins in said latch plateattached to said ram are oriented at right angles to the said latch pinsin the said latch plate attached to said hydraulic cylinder.
 4. A chainjack according to claim 1 in which said latch pins are cylindrical withflattened surfaces at their areas of contact with the surfaces of thelinks of said chain.